UI: file picker should only display yaml files and folders

[tepene]

Describe the feature

Since the introduction of configuration examples. The file pickers shows all data. I disabled the filtering for yaml files since it also blocked the examples folder. I need more time to rewrite the filter mechanism so it will show all yaml files and also all folders.

[tepene]

files to look at: https://github.com/ublue-os/forge/blob/main/anvil/nicegui/utils/filepicker.py and https://github.com/ublue-os/forge/blob/main/anvil/nicegui/pages/ansible.py